Lane deviation prevention control device for vehicle

1. A lane deviation prevention control device for vehicle, the lane deviation prevention control device comprising: a target steering torque calculator configured to calculate target steering torque to be applied to a steering system of an own vehicle in a lane deviation prevention control, the lane deviation prevention control including preventing the own vehicle from deviating from a lane on which the own vehicle is traveling; a friction torque estimator configured to estimate friction torque of the steering system; a friction compensation rate variable controller configured to perform, on a basis of steering torque produced by a driver's steering operation and on a basis of a traveling state of the own vehicle, a variable control of an addition rate at which the friction torque is added to the target steering torque to compensate friction in the steering system; and a limit processor configured to perform rate limit processing, the rate limit processing including reducing a speed of change in the target steering torque, wherein the friction compensation rate variable controller performs the variable control of the addition rate at which the friction torque is added to the target steering torque subjected to the rate limit processing in the limit processor.

2. The lane deviation prevention control device for vehicle according to claim 1 , wherein the friction compensation rate variable controller allows the addition rate to be able to vary solely toward an increase, and refrains from permitting the addition rate to vary toward a decrease.

3. The lane deviation prevention control device for vehicle according to claim 1 , wherein the friction compensation rate variable controller performs the variable control of the addition rate of the friction torque, on the basis of the steering torque produced by the driver's steering operation, on a basis of a vehicle speed of the own vehicle, and on a basis of a curvature of the lane.

4. The lane deviation prevention control device for vehicle according to claim 2 , wherein the friction compensation rate variable controller performs the variable control of the addition rate of the friction torque, on the basis of the steering torque produced by the driver's steering operation, on a basis of a vehicle speed of the own vehicle, and on a basis of a curvature of the lane.

5. The lane deviation prevention control device for vehicle according to claim 1 , wherein the lane deviation prevention control includes making a switchover between a deviation suppression control and a posture decision control, the deviation suppression control including suppressing lane deviation, and the posture decision control including controlling a posture of the own vehicle after the deviation suppression control until an arrival at a location of an end of the lane deviation prevention control, the friction compensation rate variable controller calculates, on a basis of the friction torque estimated in the friction torque estimator, friction torque during the deviation suppression control and friction torque during the posture decision control, and the friction compensation rate variable controller further performs a variable control of an addition rate at which the friction torque during the deviation suppression control is added to the target steering torque, and makes constant an addition rate at which the friction torque during the posture decision control is added to the target steering torque.

6. The lane deviation prevention control device for vehicle according to claim 2 , wherein the lane deviation prevention control includes making a switchover between a deviation suppression control and a posture decision control, the deviation suppression control including suppressing lane deviation, and the posture decision control including controlling a posture of the own vehicle after the deviation suppression control until an arrival at a location of an end of the lane deviation prevention control, the friction compensation rate variable controller calculates, on a basis of the friction torque estimated in the friction torque estimator, friction torque during the deviation suppression control and friction torque during the posture decision control, and the friction compensation rate variable controller further performs a variable control of an addition rate at which the friction torque during the deviation suppression control is added to the target steering torque, and makes constant an addition rate at which the friction torque during the posture decision control is added to the target steering torque.

7. The lane deviation prevention control device for vehicle according to claim 3 , wherein the lane deviation prevention control includes making a switchover between a deviation suppression control and a posture decision control, the deviation suppression control including suppressing lane deviation, and the posture decision control including controlling a posture of the own vehicle after the deviation suppression control until an arrival at a location of an end of the lane deviation prevention control, the friction compensation rate variable controller calculates, on a basis of the friction torque estimated in the friction torque estimator, friction torque during the deviation suppression control and friction torque during the posture decision control, and the friction compensation rate variable controller further performs a variable control of an addition rate at which the friction torque during the deviation suppression control is added to the target steering torque, and makes constant an addition rate at which the friction torque during the posture decision control is added to the target steering torque.

8. The lane deviation prevention control device for vehicle according to claim 4 , wherein the lane deviation prevention control includes making a switchover between a deviation suppression control and a posture decision control, the deviation suppression control including suppressing lane deviation, and the posture decision control including controlling a posture of the own vehicle after the deviation suppression control until an arrival at a location of an end of the lane deviation prevention control, the friction compensation rate variable controller calculates, on a basis of the friction torque estimated in the friction torque estimator, friction torque during the deviation suppression control and friction torque during the posture decision control, and the friction compensation rate variable controller further performs a variable control of an addition rate at which the friction torque during the deviation suppression control is added to the target steering torque, and makes constant an addition rate at which the friction torque during the posture decision control is added to the target steering torque.

9. A lane deviation prevention control device for vehicle, the lane deviation prevention control device comprising circuitry configured to calculate target steering torque to be applied to a steering system of an own vehicle in a lane deviation prevention control, the lane deviation prevention control including preventing the own vehicle from deviating from a lane on which the own vehicle is traveling, estimate friction torque of the steering system, performs, on a basis of steering torque produced by a driver's steering operation and on a basis of a traveling state of the own vehicle, a variable control of an addition rate at which the friction torque is added to the target steering torque to compensate friction in the steering system, and performs rate limit processing, the rate limit processing including reducing a speed of change in the target steering torque, wherein the variable control of the addition rate at which the friction torque is added to the target steering torque subjected to the rate limit processing in the limit processor is performed.